1. Field of the Invention
The present invention relates to a drawing apparatus for fixing a sheet-shaped recording material to an outer peripheral surface of a drum to draw an image on the recording material.
2. Description of the Background Art
Drawing apparatuses have been used for drawing images upon irradiation of various types of photosensitive materials with light. In a drum-type drawing apparatus, a photosensitive material is mounted on a recording drum which is rotatable in a primary scanning direction, and a recording head comprising a laser diode and the like moves in a secondary scanning direction parallel to a rotary shaft of the recording drum to draw an image on the photosensitive material.
FIG. 34 is a schematic perspective view of a recording drum in a conventional drawing apparatus. A plate 160 made of aluminum serving as a photosensitive material is mounted on a recording drum 150 shown in FIG. 34. A front end clamp 170 for fixing one end of the plate 160 and a rear end clamp 180 for fixing the other end of the plate 160 are attached to an outer peripheral surface of the recording drum 150. The rear end clamp 180 contains a magnet, and is fixed by a magnetic force to a position, on the outer peripheral surface of the recording drum 150, corresponding to the size of the plate 160.
The recording drum 150 having the plate 160 attached thereto is rotated at relatively low speed around a rotary shaft 190, so that an image is drawn on the surface of the plate 160.
In recent years, a request to improve the efficiency of processing for drawing an image on the plate 160 has been made. In order to improve the efficiency of the drawing processing, the recording drum 150 having the plate 160 attached thereto must be rotated at high speed.
However, the rear end clamp 180 is fixed to the recording drum 150 by the magnetic force. When the recording drum 150 is rotated at high speed, therefore, the rear end clamp 180 moves on the outer peripheral surface of the recording drum 150 or is detached from the recording drum 150, so that the plate 160 fixed to the recording drum 150 may be shifted in position and detached. Therefore, the recording drum 150 cannot be rotated at high speed.
An object of the present invention is to provide a drawing apparatus capable of reliably fixing a sheet-shaped recording material of arbitrary size to an outer peripheral surface of a cylindrical drum.
Another object of the present invention is to provide a drawing apparatus capable of uniformly bringing a sheet-shaped recording material into close contact with an outer peripheral surface of a cylindrical drum.
A drawing apparatus according to one aspect of the present invention for drawing an image on a sheet-shaped recording material comprises a cylindrical drum having a rotary shaft and an outer peripheral surface and having a groove extending in the circumferential direction provided on the outer peripheral surface, a rotation driving device for rotating the drum around the rotary shaft, a fixing member provided so as to be attachable and detachable to or from the groove of the drum and so as to be movable along the groove for fixing the recording material to the outer peripheral surface of the drum, and a drawing unit for drawing an image on the recording material fixed on the outer peripheral surface of the drum, the fixing member comprising a main body member having one side part for pressing one end of the recording material against the outer peripheral surface of the drum, an engaging member provided so as to project on the side of the lower surface of the main body member and engaged with the inside of the groove of the drum, and urging means for urging the other side part of the main body member in the direction away from the outer peripheral surface of the drum.
In the drawing apparatus, the fixing member is provided so as to be attachable and detachable to or from the groove of the cylindrical drum and so as to be movable along the groove. The sheet-shaped recording material is mounted on the outer peripheral surface of the drum, and is fixed by the fixing member.
The engaging member provided in the main body member of the fixing member is engaged with the inside of the groove of the drum, thereby making it possible to fix the fixing member to the drum. The one end of the recording material is interposed between the one side part of the main body member and the outer peripheral surface of the drum, and the other end of the main body member is urged in the direction away from the outer peripheral surface of the drum by the urging means. Thus, the one end of the recording material is pressed against the outer peripheral surface of the drum by the one side part of the main body member. In this state, the drum having the recording material fixed thereto can be rotated around the rotary shaft by the rotation driving device.
The engaging member can be released from the groove of the drum by releasing the engagement of the engaging member provided in the fixing member. Thus, the fixing member can be moved in the circumferential direction along the groove on the outer peripheral surface of the drum. Consequently, the recording material of arbitrary size can be reliably fixed to the outer peripheral surface of the drum.
It is preferable that the length of the one side part of the main body member which is determined on the basis of the engaging member in the circumferential direction of the drum is smaller than the length of the other side part of the main body member.
In this case, at the time of rotation of the drum, centrifugal forces are exerted, respectively, on the one side part and the other side part of the fixing member. Since the length of the one side part of the main body member is smaller than the length of the other side part of the main body member, a rotation moment generated by the one side part of the main body member centered around the engaging member is smaller than a rotation moment generated by the other side part of the main body member, so that a force is exerted in the direction in which the other side part of the main body member separates from the outer peripheral surface of the drum. As a result, the one end of the recording material is firmly pressed against the outer peripheral surface of the drum by the one side part of the main body member.
The higher the rotational speed of the drum is, the larger the force to separate the other end of the main body member from the outer peripheral surface is, and the larger a force for the one side part of the main body member to press the one end of the recording material against the other peripheral surface of the drum is. Even when the drum is rotated at high speed, therefore, the recording material on the outer peripheral surface of the drum is not shifted in position and detached.
A weight may be provided in the other side part of the main body member. In this case, at the time of rotation of the drum, a centrifugal force is exerted on the weight provided in the other side part of the main body member, and a force is exerted in the direction in which the other side part of the main body member separates from the outer peripheral surface of the drum. As a result, the one end of the recording material is firmly pressed against the outer peripheral surface of the drum by the one side part of the main body member.
The higher the rotational speed of the drum is, the larger the centrifugal force exerted on the weight on the other side part of the main body member is, and the larger the force for the one side part of the main body member to press the one end of the recording material against the outer peripheral surface of the drum is. Even when the drum is rotated at high speed, therefore, the recording material on the outer peripheral surface of the drum is not shifted in position and detached.
The urging means may comprise a spring provided between a lower surface of the other side part of the main body member and the outer peripheral surface of the drum, and the weight may be a metal provided in the spring.
In this case, the other side part of the main body member is urged in the direction away from the outer peripheral surface of the drum by a reaction force produced by the spring. In addition, at the time of rotation of the drum, the metal provided in the spring presses the other side part of the main body member in the direction away from the outer peripheral surface of the drum by a centrifugal force. Thus, the one end of the recording material is firmly pressed against the outer peripheral surface of the drum by the one side part of the main body member.
The urging means may comprise a spring provided between the lower surface of the other side part of the main body member and the outer peripheral surface of the drum.
The drawing apparatus may further comprise a fixing member driving device for operating the engaging member of the fixing member to fix the fixing member to the drum or release the fixing member from the drum.
In this case, the engaging member of the fixing member is operated by the fixing member driving device, so that the fixing member can be fixed to the drum or released from the drum. Consequently, it is possible to fix the fixing member to the drum and easily release the fixing member from the drum.
The fixing member driving device may hold the fixing member in a state where the engaging member of the fixing member is released from the groove of the drum.
In this case, the fixing member is held by the fixing member driving device when the engaging member of the fixing member is released from the groove of the drum, thereby making it easy to attach the fixing member to the drum and detach the fixing member from the drum.
The engaging member may be a rotating member provided so as to be rotatable in the main body member and fixed in the groove of the drum as it rotates.
In this case, the rotating member provided in the main body member of the fixing member is rotated, so that the rotating member can be fixed in the groove of the drum. In addition, the rotating member provided in the fixing member is rotated, so that the rotating member can be released from the groove of the drum. Thus, the fixing member can be moved in the circumferential direction along the groove on the outer peripheral surface of the drum.
The fixing member may further comprise a sliding member provided in the main body member so as to be slidable in a predetermined direction for rotating the rotating member as it slides, and the fixing member driving device may comprise a driving member engaged with the sliding member in the fixing member, and a driving member driving mechanism for moving the driving member in the predetermined direction.
In this case, the driving member of the fixing member driving device is engaged with the sliding member in the fixing member, and the driving member is moved in a predetermined direction by the driving member driving mechanism, so that the sliding member in the fixing member can be slid with respect to the main body member to rotate the rotating member. Thus, the rotating member in the fixing member can be fixed in the groove of the drum, or the rotating member in the fixing member can be released from the groove of the drum.
The driving member driving mechanism may comprise a moving member which together with the driving member, moves in the predetermined direction, and the fixing member driving device may further comprise a holding member for holding or releasing the main body member of the fixing member as the moving member moves.
In this case, the moving member in the fixing member driving device is moved, so that the main body member of the fixing member can be held by the fixing member or released. Thus, it is possible to hold the fixing member by the fixing member driving device when the rotating member of the fixing member is released from the groove of the drum and detach the fixing member from the fixing member driving device when the rotating member of the fixing member is fixed in the groove of the drum. Consequently, it is possible to easily attach the fixing member to the drum and detach the fixing member from the drum.
The engaging member may be a lock member having a press portion and an lock portion, the lock portion being insertable into the groove of the drum as the press portion is pressed, while being locked into the groove by releasing the pressing of the press portion.
In this case, the press portion of the lock member provided in the main body member of the fixing member is pressed, so that the lock portion of the lock member can be inserted into the groove of the drum. In addition, the pressing of the press portion of the lock member is released, so that the lock portion is locked into the groove of the drum. Thus, the fixing member can be fixed to the drum. Further, the press portion of the lock member provided in the fixing member is pressed, thereby making it possible to release the locking of the lock portion of the lock member in the groove of the drum. Thus, the fixing member can be moved in the circumferential direction along the groove on the outer peripheral surface of the drum.
The fixing member driving device may comprise a driving device for pressing the press portion of the lock member of the fixing member, and a driving member driving mechanism for moving the driving member toward the press portion of the lock member.
In this case, the driving member in the fixing member driving device is moved toward the press portion of the lock member by the driving member driving mechanism, thereby making it possible to press the press portion of the lock member by the driving member. Thus, it is possible to insert and lock the lock portion of the lock member into the groove of the drum or release the locking of the lock portion of the lock member in the groove of the drum.
The fixing member driving device may comprise a supporting member and a sliding member provided so as to be slidable in a predetermined direction with respect to the supporting member for moving the driving member toward the press portion of the lock member as it slides.
In this case, the sliding member in the fixing member driving device is slid in a predetermined direction with respect to the supporting member, thereby making it possible to move the driving member toward the press portion of the lock member. Thus, the driving member can press the press portion of the lock member.
The fixing member driving device may further comprise a holding member for holding or releasing the main body member of the fixing member as the sliding member slides.
In this case, the sliding member of the fixing member driving device is slid, so that the main body member of the fixing member can be held by the holding member or released. Thus, the fixing member can be held by the fixing member driving device when the lock member of the fixing member is released from the groove of the drum, the fixing member can be detached from the fixing member driving device when the lock member of the fixing member is locked into the groove of the drum. Consequently, it is possible to easily attach the fixing member to the drum and detach the fixing member from the drum.
The lock member may comprise first and second lock members having a press portion and a lock portion, a shaft for connecting the first and second lock members to each other so as to be rotatable, and a spring member for urging the first and second lock members in the direction in which the lock portion of each of the first and second lock members is locked into the groove of the drum, and the first and second lock members may be provided such that the locking of the lock portion in the groove is released by the pressing of the press portion.
The drawing apparatus may further comprise a strip-shaped lock plate provided in the groove of the drum, the spring member may urge the first and second lock members in the direction in which the lock portion of each of the first and second lock members is locked into the lock plate, and the first and second lock members may be provided such that the locking of the lock port ion by the lock plate is released by the pressing of the press portion.
The drawing apparatus may further comprise a moving mechanism for moving the fixing member driving device to a position spaced apart from the outer peripheral surface of the drum and a position in close proximity to the outer peripheral surface of the drum.
In this case, the fixing member driving device can be moved to the position spaced apart from the outer peripheral surface of the drum and the position in close proximity to the outer peripheral surface of the drum by the moving mechanism, thereby making it possible to smoothly attach the fixing member to the drum and detach the fixing member from the drum.
A drawing apparatus according to another aspect of the present invention for drawing an image on a sheet-shaped recording material comprises a cylindrical drum having a rotary shaft and an outer peripheral surface, a rotation driving device for rotating the drum around the rotary shaft, a fixing member provided on the outer peripheral surface of the drum for fixing the recording material on the outer peripheral surface of the drum, a drawing unit for drawing an image on the recording material fixed on the outer peripheral surface of the drum, a first roller arranged along the outer peripheral surface of the drum parallel to the rotary shaft of the drum, a second roller arranged along the first roller, and a roller moving mechanism for moving the first roller to a position spaced apart from the outer peripheral surface of the drum and the second roller and a position in contact with the outer peripheral surface of the drum and the second roller.
In the drawing apparatus, the sheet-shaped recording material is fixed on the outer peripheral surface of the cylindrical drum by the fixing member. In this state, the drum having the recording material fixed thereto can be rotated around the rotary shaft by the rotation driving device.
When the first roller is moved to the position in contact with the outer peripheral surface of the drum and the second roller by the roller moving mechanism, the first roller uniformly presses the recording material fixed on the outer peripheral surface of the drum. Thus, the recording material on the outer peripheral surface of the drum is uniformly brought into close contact with the outer peripheral surface of the drum.
In addition, dust or the like which adheres to the surface of the recording material on the outer peripheral surface of the drum is transferred to the first roller, and the dust or the like which has been transferred to the first roller is transferred to the second roller. Thus, it is possible to remove the dust or the like from the recording material on the outer peripheral surface of the drum.
When the first roller is moved to the position spaced apart from the outer peripheral surface of the drum and the second roller by the roller moving mechanism, the recording material on the outer peripheral surface of the drum is released from the first roller. At this time, the first roller is also spaced apart from the second roller, so that the dust or the like which has been transferred to the second roller is not transferred to the first roller again.
A drawing apparatus according to still another aspect of the present invention for drawing an image on a sheet-shaped recording material comprises a cylindrical drum having a rotary shaft and an outer peripheral surface and having a groove extending in the circumferential direction provided on the outer peripheral surface, a rotation driving device for rotating the drum around the rotary shaft, a first fixing member provided on the outer peripheral surface of the drum for fixing one end of the recording material on the outer peripheral surface of the drum, a second fixing member provided so as to be attachable and detachable to or from the groove of the drum and so as to be movable along the groove for fixing the other end of the recording material on the outer peripheral surface of the drum, a drawing unit for drawing an image on the recording material fixed on the outer peripheral surface of the drum, a first roller arranged along the outer peripheral surface of the drum parallel to the rotary shaft of the drum, a second roller arranged along the first roller, and a roller moving mechanism for moving the second roller to a position spaced apart from the outer peripheral surface of the drum and the second roller and a position in contact with the outer peripheral surface of the drum and the second roller.
The second fixing member may comprise a main body member having one side part for pressing the other end of the recording material against the outer peripheral surface of the drum, an engaging member provided so as to project on the side of the lower surface of the main body member and engaged with the inside of the groove of the drum, and urging means for urging the other side part of the main body member in the direction away from the outer peripheral surface of the drum.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.